Idea for a piezo electric generator.
A saturated water solution of rochelle salt (seignette salt, wine stone, kali hydrogenotartas), that builds piezoelectric crystals,
I put some fine wooden sawdust into the solution.
Already prepared is a copper sheet that was heated, so the surface is covered by cupric oxide, that has semiconductive properties.
I put the soaked sawdust onto the curic oxid layer and let it dry. Crystals form between copper and sawdust.
I add a steel grid ontop of the sawdust layer, so the whole thing is under pressure, but the air can still reach the sawdust.
Now, what I expext to happen is: during chanches in Humidity of the air, the sawdust is constantly expanding or contracting, causing a voltage on affected crystals. The semiconductive Coppersheet finally half-rectifies this voltage.
By using a simple mechanism that is causing alternating levels of humidity/moisture, the efficiency could be increased.
This is not a kw generator and no energy from an unknown source, and it is most likely a tiny source, but it's very real and very doable. Unlike the cement battery, this one will last for years. If fungicides are added, propably for centuries.
Just for the records...
Didn't work so far. Semiconducting cupric oxide: not yet managed to create this, maybe on a camp fire one day. Instead I chose 2 Aluminum modquito meshes, applied a voltage to them while the rochelle salt was crystalizing between them, hoping to get a bipolar crystalisation. Nope, but the bottom Aluminum mesh was higly corroded, disappeared by about 50% of it.
After drying, volts zero, amps zero. Rochelle Salt is however useful for piezoelectric experiments and for crystal growing (which is a bit of a science by its own, but I've seen monocrystals in the size of an apple, just google it).